Heparin, which is an anticoagulant, is used to avoid blood coagulation during the treatment of thromboembolism or disseminated intravascular coagulation (DIC), dialysis, or extracorporeal circulation.
However, it is known that the administration of heparin sometimes causes HIT (heparin-induced trombocytopenia), and the responsible factor is considered to be the generation of an autoantibody (HIT antibody) against platelet factor 4 (PF4) to which heparin binds. The diagnosis of HIT is carried out by measuring the production of the HIT antibody. More particularly, the HIT antibody strongly reacts with heparin/PF4, but hardly reacts with PF4, and therefore, an ELISA (Enzyme-Linked ImmunoSorbent Assay) method in which a human plasma sample is reacted with a heparin/PF4 complex immobilized on a plate, followed by an enzyme-labeled anti-human-immunoglobulin antibody, and an enzyme reaction is carried out to determine the presence or absence of the HIT antibody is known (Non-patent references 1 to 3).
However, the HIT antibody contained in samples is merely qualitatively or semi-quantitatively measured by absorbance (OD value) in these references.